Foam molding of plasticized polyurethane foam for an automotive seat pad, for example, is performed by introducing an undiluted urethane solution into a mold and foaming the same in the mold. The mold generally has an upper mold and a lower mold.
I. Japanese Unexamined Utility Model Registration Application Publication No. 62-185015 discloses a packing seal provided between mating surfaces of the upper mold and the lower mold.
FIG. 11 is a cross-sectional view of a packing seal portion according to Japanese Unexamined Utility Model Registration Application Publication No. 62-185015. A lower mold 40 has a mating surface 41 provided with a groove 42 which has a circular arc shape in cross section. A packing seal 50 has a lower portion 51 fitted into the groove 42.
The packing seal has an upper portion protruding above the mating surface 41 and thereby forms a sheet portion 52 which spreads over the mating surface 41. It is noted that the sheet portion 52 has a part provided with a protrusion 53.
II. Japanese Unexamined Utility Model Registration Application Publication No. 6-42130 also discloses a groove provided in a mating surface of a lower mold, wherein the groove has a circular arc shape in cross section.
FIG. 12 is a cross-sectional view illustrating the vicinity of a mating surface of a lower mold according to Japanese Unexamined Utility Model Registration Application Publication No. 6-42130. A lower mold 61 has a mating surface provided with a groove 62 which has a circular arc shape in cross section, and a packing seal 63 having a circular shape in cross section is fitted into the groove 62. The packing seal has an upper portion protruding above the mating surface of the lower mold 61.
Patent literature 1: Japanese Unexamined Utility Model Registration Application Publication No. 62-185015
Patent literature 2: Japanese Unexamined Utility Model Registration Application Publication No. 6-42130
The sheet portion 52 in Japanese Unexamined Utility Model Registration Application Publication No. 62-185015 is kept away (or, set back) from an edge 44 on the cavity 43 side. Therefore, in the state where the mold is clamped, there is a gap between the mating surfaces from their edges on the cavity 43 side down to the sheet portion 52.
In the case where this mold is used for molding a seat pad, if there is any portion exhibiting poor airtightness between the upper mold and the packing seal 50, urethane will penetrate into between the mating surfaces and thereby form burrs.
Such burrs need to be removed manually after the demolding process, thereby making the production of the seat pads or other molded products troublesome and costly.
Furthermore, referring to FIG. 11, the groove 42 has an approximately circular shape in cross section. Thus, if the groove 42 is formed too close to the cavity 43, the lower mold 40 between the groove 42 and the cavity 43 will be reduced in thickness, which leads to an insufficient strength and also gives rise to a need for an unnecessary high processing accuracy. It is thus necessary to keep the groove 42 away from the cavity 43 to a certain extent, resulting in a large distance between the sheet portion 52 and the cavity 43.
In Japanese Unexamined Utility Model Registration Application Publication No. 6-42130 as well, the groove 62 and the packing seal 63 fitted into the groove 62 are kept away from the cavity side edge of the mating surface of the lower mold 61.
Particularly, the packing seal 63 has no portion equivalent to the sheet portion 52 provided in Japanese Unexamined Utility Model Registration Application Publication No. 62-185015, and a larger gap is thereby produced between the mating surfaces from their cavity side edges down to the packing seal 63.
Therefore, in the case where the mold of Japanese Unexamined Utility Model Registration Application Publication No. 6-42130 is used for molding a seat pad, there will be a greater amount of urethane that will penetrate into between the mating surfaces and thereby form burrs than in the case of using the mold of Japanese Unexamined Utility Model Registration Application Publication No. 62-185015.